According to Section 51.942 of the Texas Education Code each tenured faculty shall receive a comprehensive performance peer evaluation by department and school/college promotion and tenure committees no less often than once every six (6) years following the last tenure, promotion, or post-tenure performance.
Please see the links below which detail the process:
Post-Tenure Review - Article XI of Faculty Bylaws
Post-Tenure Review Timeline 2012
Criteria
Promotion and Tenure Committees